It is known to use a honeycomb-shaped substrate having a washcoat thereon which includes a zeolite or equivalent material which is coated or impregnated with a palladium catalyst. Such devices are very useful in converting hydrocarbon constituents in the exhaust gas from a combustion engine. However, under relatively high flow conditions, such devices have hydrocarbon converging efficiencies of less than 50 percent during the first 140 seconds of operation of the combustion engine. This is undesirable because the system does not meet Federal emission standards.
The present invention provides advantages over the prior art.